The present invention relates to a scroll compressor, which may be used as an air compressor or coolant compressor.
FIGS. 1A through 1D show the essential components of a scroll compressor. In these figures, reference numeral 1 designates a stationary scroll, 2 an oscillating scroll, 3 a discharge port, 4 a compression chamber, O a fixed point on the stationary scroll, and O' a fixed point on the oscillating scroll. The stationary scroll 1 and the oscillating scroll 2 have a complementary spiral configuration in cross section. More specifically, each scroll is made, for instance, involuted in cross section, according to a technique well known in the art.
The operation of the scroll 1 compressor will be described. As shown in FIGS. 1A through 1D, the scroll is held stationary while the scroll 2 is oscillated in an orbiting motion with its angular orientation maintained unchanged. Positions of the two scrolls at angles of 0.degree., 90.degree., 180.degree. and 270.degree. of the 360.degree. cycle of movement thereof are indicated in FIGS. 1A through 1D, respectively. As the scroll 2 moves through this cycle, the volumes of crescent-shaped compression chambers 4 formed by the scrolls 1 and 2 first decrease, at which time the air (or other fluid) taken into the compression chambers is compressed. Then the air is discharged through the discharge port 3. In this operation, the distance OO' between the fixed points O and O' is maintained unchanged. That is, EQU OO'=p/2-t,
where p is the gap width between the spiral structures (corresponding to the pitch of the spiral curve) and t is the thickness of the spiral arms of the scrolls.
An example of a conventional coolant compressor operating in accordance with the above-described principle will be described with reference to FIG. 2. In FIG. 2, reference numeral 1 designates a stationary scroll, 2 an oscillating scroll, 3 a discharge port, 4 a compression chamber, 5 a main shaft, 6 a lubricating hole formed in the main shaft, 7 and 8 bearing frames, 9 a motor rotor, 10 a motor stator, 11 a housing, 12 an Oldham coupling, 13 a baffle plate, 14 an oil pool formed at the bottom of the housing 1, 15 a coolant gas intake pipe, 16 a discharge pipe, 17 an oscillating bearing formed eccentically in the main shaft and engaged with an oscillating scroll shaft 2a, 18 a main bearing fitted on the upper portion of the main shaft 5, 19 a motor bearing fitted on the lower portion of the main shaft 5, 20 and 21 oil return holes of an oil path, 22 and 23 communicating holes of a gas suction path, and 24 a suction hole of the gas suction path.
The stationary scroll 1 is secured to the bearing frame 7 with screws. The shaft 2a of the oscillating scroll 2 is engaged with the main shaft 5. The main shaft 5 is rotatably supported by the bearing frames 7 and 8, which are coupled to one another by means of a faucet joint or the like. The motor rotor 9 is fixedly secured to the main shaft 5 by press fitting or shrink fitting or with screws. The motor stator 10 is fixedly secured to the bearing frame 8 in the same manner. The Oldham coupling 12, arranged between the oscillating scroll 2 and the bearing frame 7, prevents rotation of the oscillating scroll 2. The above components are housed in the housing 11.
The operation of the scroll compressor thus assembled will be described. When the motor rotor 9 rotates, the rotary motion of the rotor 9 is transmitted through the shaft 5 as is converted to orbital motion of the oscillating scroll 2 by means of bearings 17, 18; that is, the oscillating scroll 2 is orbited, as a result of which compression is started according to the operating principle described with reference to FIGS. 1A through 1D. In this operation, the coolant gas is sucked into the compressor through the intake pipe, flowing through communication hole 22, the motor air gap, etc. to cool the motor. Thereafter, the coolant gas is introduced through the communication hole 23 and the suction hole 4 of the stationary scroll 1 into the compression chamber 4 where it is compressed. The compressed gas is discharged from the compressor through the discharge port 3 and the discharge pipe 16. The lubricant from the oil pool 14 passes through the lubricating hole 6 formed in the main shaft 5 and from there is supplied to the sliding parts of the bearings 17, 18 and 19 by a centrifugal pumping action. The lubricant is returned to the oil pool 14 through the oil return holes 20 and 21 in the bearing frames 7 and 8. To prevent lubricant dripping from the sliding parts of the bearings 17 and 18 from being sucked directly into the compression chamber 4, the baffle plate 13 is provided to separate the compression chamber from the sliding mechanism.
In the conventional scroll compressor described above, lubricant discharged through the oil return hole 21 is liable to be atomized upon meeting the gas flowing through the communication hole 22, etc., and hence a portion of the lubricant passing through the communication hole 23 is liable to be sucked into the compression chamber 4 together with the intake gas. Furthermore, when the compressor is started, frequently coolant gas mixed with the lubricant in the oil pool 14 causes the lubricant to foam, as a result of which gas and lubricant are sucked together through the hole 23 into the compression chamber 4 and are then discharged. In such a case, the compressor may quickly be depleted of lubricant. As a result, the compressor may not be sufficiently lubricated and the bearings may be damaged or they may seize.